This invention relates generally to turbines. In one aspect, the invention relates to steam turbines in which pressurized steam is employed to drive a turbine wheel.
A common type of steam turbine employs a plurality of circularly cross-sectioned nozzles circumferentially spaced around the interior of a turbine housing and oriented so as to drive the turbine wheel. The design is inherently inefficient but is widely used, because a turbine which employs drilled or pipe type nozzles is much less expensive to manufacture than a more efficient design which utilizes airfoils to distribute the steam against the wheel.
Converting these older units to a more efficient design would result in substantial savings in steam. For example, a modification to convert a unit from a drilled or pipe-type inlet system to an airfoil type inlet system could result in a 15% savings in steam consumption, while producing the same amount of power, with reductions up to 30% being possible under certain steam conditions. Because of the size of the units, a conversion to a more efficient design could result in savings on fuel costs on the order of $200,000 per year that the unit is operated.
It is an object of this invention to provide such a conversion that is cost effective to implement.
In one embodiment of the invention, there is provided a turbine which includes a turbine case, a turbine shaft, a turbine wheel, a louver, and a housing for connecting the louver to the turbine case. The turbine case has a first end wall, a second end wall, and a peripheral side wall connecting the first end wall and the second end wall. The turbine case defines a turbine chamber. The turbine shaft is rotatably mounted in the turbine case and extends between the first end wall and the second end wall of the turbine case. The turbine shaft has a longitudinal axis. The turbine wheel is attached to the turbine shaft and extends radially from the shaft. The turbine wheel is positioned in the turbine chamber between the first end wall and the second end wall of the turbine case. The turbine wheel has a turbine wheel periphery which is positioned adjacent to the peripheral sidewall of the turbine case. The turbine case defines a plurality of inlet ports opening through the first end wall to a location in the turbine chamber which is adjacent to the peripheral sidewall of the turbine case. The inlet ports open into the turbine chamber in a direction which is parallel to the longitudinal axis of the turbine shaft. The louver is arcuately shaped and is for directing fluid against the periphery of the turbine wheel so as to cause rotation of the turbine wheel. The adapter housing extends from the arcuately shaped louver to the first end wall of the turbine case and locates the arcuately shaped louver and forms a fluid flow path from the inlet ports to the arcuately shaped louver.
In another embodiment of the invention, there is provided an improvement to a process in which a flow of gas is introduced into a turbine case through a plurality of peripherally spaced passages formed by an end wall of the turbine case, the passages opening through the end wall of the case in a direction generally parallel to the turbine shaft. The improvement is provided by flowing the gas from the outlets of the passages into an arcuately shaped housing mounted in covering relationship with the outlets, and thence through a louver for impingement on the periphery of the turbine wheel.
In a further embodiment of the invention, there is provided a method for modifying a steam turbine of the type which incorporates a turbine case defining a plurality of passages having outlets opening through an inside end wall of the turbine case in a direction generally parallel to the turbine shaft, with nozzles positioned over the outlets to direct steam against the periphery of the turbine wheel. To perform the modification, the nozzles are removed, an arcuately shaped housing is positioned in covering relationship with the outlets, and an arcuately shaped louver is positioned so as to form an end wall of the housing. The louver has a plurality of vanes to direct the steam against the periphery of the turbine wheel to cause rotation of the turbine shaft and the housing forms a confined steam flow path from the outlets to the louver. Greater efficiency can be obtained by employing the louver instead of nozzles, and the invention thus provides a technique for modifying a common steam turbine design to provide a more efficient unit.